Looking back on Game of Thrones, it appears that Bran had been plotting to be king since season 4. It came as quite a shock when Bran was elected the new king of Westeros. For most of the show's run, many fans assumed Jon Snow or Daenerys Targaryen would rule over the Seven Kingdoms. While Arya Stark ending up as ruler would have been the kind of subversion the show was known for, Bran was far from the top of most people's predictions. Even Isaac Hempstead-Wright, who plays Bran, thought his character's fate was a joke.
After Daenerys became The Mad Queen, however, Jon Snow was forced to kill her in order to protect the realm from her rage. As a result, Jon effectively relinquished his claim to the Iron Throne as the Dothraki and Unsullied would never allow him to rule, and neither would many of the lords and ladies of Westeros. And so, he was forced to once again join the Night's Watch. Last seen journeying beyond the Wall with Tormund and Ghost, any chance of Jon ruling Westeros was officially quashed.
As such, it fell upon a council of surviving characters - potentially including Howland Reed - to vote on a new ruler. After a speech from Tyrion Lannister, it was decided that Bran Stark would be crowned. While that came as a surprise to fans across the world, Bran's story has actually been building to this since Game of Thrones season 4. And the character was actually contributing towards that end even before the final season.
Bran Saw Season 8 In Season 4
As soon as Bran touched the weirwood tree north of the Wall, he experienced a flurry of visions. Those visions were primarily focused on the Three-Eyed Raven's location. Among them, however, were images of the Mad King's final moments, the vision that Daenerys experienced in the House of the Undying, and a dragon flying over King's Landing. On the surface, they appeared to be visions of the past. An identical shot of Drogon in "The Bells" reveals, however, that what Bran saw was actually the future. More specifically, it was the final episodes of Game of Thrones season 8. At the time, Bran couldn't fully comprehend what he was seeing. Much like the audience, he experienced it in fragments. That is largely the reason he continued North, to learn how to harness his powers.
Most of Bran's training in season 6 was spent observing the past. He was told he couldn't interact, yet later events appear to contradict that. Such contradictions began when a younger version of Ned Stark seemingly heard him. They culminated with the Night King making physical contact via Bran's projected consciousness and, more tragically, when he broke Hodor's mind in the past and doomed the gentle giant.
Although the previous Three-Eyed Raven claimed that such things shouldn't be possible, Bran proved otherwise. As Jojen Reed teased when Bran first warged into Hodor, he was capable of things nobody previously was able to. And if he was able to see into and interact with the past, then why would witnessing and shaping the future be any different? Whether Bran knew what was coming has been highly discussed in the wake of season 8, especially given that he implied that becoming king was the reason he traveled to King's Landing. In truth, however, Bran could always see the future. As far back as season 1, Bran experienced dreams that predicted future events. He saw Ned Stark in the Winterfell crypts, prior to his death. And he dreamt "that the sea came to Winterfell" - which symbolized Theon Greyjoy's betrayal. Bran could always see the future, but it wasn't until training with the Three-Eyed Raven that Bran could consciously control his abilities.
What Was Bran’s Plan?
Once Bran had control of his powers, it was clear that he knew the sequences of events that led to desirable outcomes and he could guide them accordingly. That was why he gave Arya the Valyrian steel dagger, helped Jaime Lannister avoid execution, and comforted Theon right before his death. All of it played a part in keeping Bran safe from the Night King.
Even before The Long Night and the Battle of Winterfell, Bran had also laid the groundwork for his ascension. Such was why he urged Sam to tell Jon the truth of his heritage at a particular time. He knew how the dominoes would fall - from Jon telling Daenerys, to Dany feeling increasingly hostile, to Sansa learning the truth and passing the information on to Tyrion. Dany stated, after the battle, that she would have been happy had she not known about Jon. Had she not, her experiences at the celebratory feast might have been different. By knowing, however, the seeds were sown. And the feast merely watered them, not only in her mind but in the faith Varys had in her. Bran's abilities would also have been of great use to Daenerys, especially in preventing Euron Greyjoy's ambush and the killing of Rhaegal. And yet, he didn't offer them, because everything was necessary to ensure Dany's downfall and his own election as king.
The Starks had numerous mentors on the show: Sansa learned from Littlefinger, and Arya learned from The Hound and Jaqen H'ghar. Bran, meanwhile, could learn from anybody about anything. In that way, he could ostensibly be the product of every great schemer that ever was. Thanks to his abilities, he was able to do what Littlefinger could only imagine. He could fight every battle everywhere and see every possible series of events all at once, in a literal sense. Before being crippled, Bran was a climber. And now he could climb the ladder in a way Littlefinger never could. All he needed was the chaos of Daenerys burning down King's Landing. It's unclear whether Bran actually wanted Daenerys to do what she did, but the overtly rational person he had become knew that it was something that needed to happen.
Jon and Tyrion were told repeatedly that Daenerys was unstable. And repeatedly, they ignored the warnings. Unfortunately, their belief was exposed as distressingly misplaced. The destruction of King's Landing, in that regard, was something they had to witness for themselves. Only then would they do what needed to be done and as Bran foresaw. Confined to a wheelchair, there was no way that Bran could have done the deed himself. Instead, it had to fall on the shoulders of one close to her and that knew first-hand the threat she posed.
What Comes Next
Given that, it could be argued that he is actually one of the show's most villainous characters. After all, he had Jon sent back North and Sansa crowned Queen of the North. Both acts could be seen as blocking rivals for his throne. Equally, letting so many people die so you may be king is Joffrey-level callousness. It would certainly be in keeping with the bittersweet nature George R.R. Martin promised - the wheel seemingly broken and in the hands of a noble soul but actually in the hands of a more cunning and dangerous leader. Such would be fitting of the ambiguity of heroes and villains that the world of Westeros cultivated in early seasons.
Then again, Game of Thrones has always explored the concept of sacrifice for the greater good. While it could be argued that Bran curtailed the threats potentially posed by Sansa and Jon, being the true heir to the throne, but it could also be seen as giving them the kind of lives they craved. As such, his plan may not have been one of ambition but necessity. He cannot share visions or guarantee that they will be believed. Also, Daenerys needed to win the throne if she was going to let her guard down enough for someone to strike the final blow. As well as enabling him to learn from people across all of history, his abilities also allow him greater insight into the common folk. In that regard, he could be everything Varys had hoped for in a ruler. He could even ostensibly end any strife before they begin. Yes, Bran's plan involved letting King's Landing be destroyed, but, in the aftermath, he's in a position to prevent any further innocent bloodshed.
Whether or not Bran can be considered a villain or a servant of the greater good will obviously be a matter of opinion and much debate - unless the idea is expanded upon in Martin's upcoming A Song of Ice and Fire books. Whatever the case, even though the show didn't go as far as to have a scene of him secretly stepping out of his wheelchair and revealing himself actually able to walk, Bran is assuredly the show's Keyser Soze. In the end, he proved himself to be the game's shrewdest player. All fans can do now is hope that he was actually on the side of good and wasn't ultimately corrupted by power in the way most other Game of Thrones characters have been.